Global distribution of crustal magnetization discovered by the Mars GlobalSurveyor MAG/ER experiment

Vector magnetic field observations of the martian crust were acquired by th e Mars Global Surveyor (MCS) magnetic field experiment/electron reflectomet er (MAG/ER) during the aerobraking and science phasing orbits, at altitudes between similar to 100 and 200 kilometers. Magnetic field sources of multi ple scales, strength, and geometry were observed. There is a correlation be tween the location of the sources and the ancient cratered terrain of the m artian highlands. The absence of crustal magnetism near large impact basins such as Hellas and Argyre implies cessation of internal dynamo action duri ng the early Naochian epoch (similar to 4 billion years ago). Sources with equivalent magnetic moments as Large as 1.3 x 10(17) ampere-meter(2) in the Terra Sirenum region contribute to the development of an asymmetrical, tim e-variable obstacle to solar wind flow around Mars.